Knife sharpening machine



Dec. 23, 1969 A. K. ALLEN KNIFE SHARPENING MACHINE 3 Sheets-Sheet lFiled June 27. 1967 I G I F i 5:51 M 4 5: H M w H yo M. M "w 1 a 5 1 M 45* a m??? 2 i ,b/ m F INVENTOR. ALTON K. ALLEN ATTORNEYS DEC. 23, 1969 LEN KNIFE SHARPENING MACHINE 3 Sheets-Sheet 2 Filed June 27, 1967 FIG"?FIG.4

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Dec. 23, 1969, A. K. ALLEN KNIFE SHARPENING MACHINE 3 Sheets-Sheet 3Filed June 27, 1967 INVENTOR. ALTON K. ALLEN M ATTORNEYS Patented Dec.23, 1969 US. Cl. 51-80 Claims ABSTRACT OF THE DISCLOSURE The knifesharpening machine comprises two parallel shafts geared for equalrotation in opposite direction. Each shaft has abrasive discs andspacers, with the abrasive discs on one shaft being slightly overlappedand interleaved with the abrasive discs on the other shaft. Such aconstruction is known, but in the present machine the discs are disposedat a slight angle to the perpendicular in order to give the same awobble motion as they are rotated by the shaft. The angle of the discson one shaft is equal but opposite in direction to the angle of thediscs on the other shaft, so that the interleaved discs wobble inunison.

BACKGROUND OF THE INVENTION It has already been suggested to useinterleaved abrasive discs for sharpening a knife which is drawnlengthwise in the crevice between the discs. Such an arrangement has thedisadvantage that the knife blade must be moved steadily andcontinuously as it is being sharpened. The knife edge may be gouged ifnot handled skillfully. It has also been suggested to provide an abrasive cylinder the periphery of which is shaped somewhat like a squarethread, the helix on one cylinder resembling a right-hand thread, andthat on the other cylinder resembling a left-hand thread, so that thethreads may be meshed as they are rotated at equal speed in oppositedirection. Such a machine has the disadvantage in that it tends to pullthe knife blade lengthwise as it is being sharpened. Also the abrasivecylinders are expensive to manufacture.

SUMMARY OF THE INVENTION The present knife sharpening machine hasabrasive discs which are overlapped and interleaved, but the discs aredisposed at a slight angle to the perpendicular in order to give them awobble motion as they are rotated by the shaft. The angle of the discson one shaft is equal but opposite in direction to the angle of thediscs on the other shaft. The shafts are rotated at the same speed andin opposite directions. The discs have a desirable motion lengthwise ofthe knife blade, and this motion is a reciprocation which is so fastthat it does interfere with holding and moving the knife as it is drawnbetween the abrasive discs.

The foregoing and additional features are described in the followingdetailed specification, which is accompanied by drawings in which:

FIG. 1 is a front elevation of a knife sharpening machine embodyingfeatures of the invention;

FIG. 2 is a partially sectioned plan view thereof;

FIG. 3 is a vertical section taken approximately on the line 33 of FIG.2;

FIG. 4 is explanatory of a modification in which the discs and spacersare cemented together;

FIG. 5 shows how the peripheries of the discs may be dressed to conformto the surface of a cylinder;

FIG. 6 is a section similar to FIG. 3, but showing another form of theinvention;

FIGS. 7 and 8 show discs having two wobble cycles;

FIGS. 9 and 10 show a modified orientation; and

FIG. 11 is explanatory of the discs in FIGS. 7-10.

Referring to the drawing, and more particularly to FIGS. 1, 2 and 3, themachine comprises two parallel shafts 12 and 14 with means gearing themfor equal rotation in opposite direction. Shaft 12 has a plurality ofabrasive discs 16 and spacers 18. Shaft 14 has a generally similarseries of abrasive discs 20 and spacers 22. The spacers are somewhatthicker than the discs so that the discs may be slightly overlapped andinterleaved, as will be clear from inspection of the drawing. The discs16 are secured to shaft 12 in parallel relation, but with areas thereofat a slight angle to the perpendicular in order to give the same awobble motion as they are rotated by the shaft. The same applies to theabrasive discs 20, but the angle of the discs 20 is in a differentdirection from the angle of the discs 16. Like areas of both sets ofdiscs are preferably disposed at the same amount of angle or departurefrom the perpendicular.

The angle is preferably such that the axial motion at the periphery of adisc is greater than the axial pitch from disc to disc. The wobble ofthe discs produces a rapid reciprocation in a direction lengthwise ofthe knife blade, the latter being shown at 24 in FIG. 1. This provides acontinuous grinding action along every part of the knife blade, withoutrequiring a skilled operator to draw the knife blade through themachine. By making the reciprocation substantial, there is an allowancefor reduction in diameter of the discs as they Wear, or when they aredressed to restore them to true cylindrical configuration from time totime.

As will be seen by reference to FIGS. 2 and 3, shafts 12 and 14 havegears 26 and 28 which are in mesh with a pair of meshing gears 30 and32. An even number of gears is employed so that the abrasive wheels 16and 20 will turn in opposite direction. This direction is preferablyupward at the knife blade, as is indicated by the arrows in FIG. 1, sothat there is no tendency to wedge the blade between the wheels.

Reverting to FIG. 3, the gears 30 and 32 are disposed below the shafts12 and 14 in order not to interfere with a knife blade as it is drawnthrough the machine. Moreover, the motor 34 driving the abrasive discsis preferably operatively connected to drive one of the lower gears, inthis case the gear 30, thereby keeping the body of the motor out of thepath of a knife blade being sharpened.

The pairs of gears used are preferably equal because the rotative speedof the two grinding cylinders must be equal. The speed of rotation maybe on the order of 1800 r.p.m.

The drawing has been simplified in certain respects. In FIG. 3 is willbe understood that the gears 26 and 28 are appropriately secured to theshafts 12 and 14, as by means of a key or a diametrical pin or a setscrew. In FIG. 2, alternate gears are shown slightly different in widthfrom the intermediate gears in order to more clearly illustrate the geartrain, but in practice the gears would have the same width. The spacingof the parts in axial direction has been exaggerated, for clarity ofillustration, and in practice the knife sharpener would be much morecompact than is suggested in FIG. 2. The bearings at the ends of theshaft have not been illustrated, it being known to use anti-frictionbearings or'selflubricating bearings, and the bearings would beappropriate to prevent axial movement of the shafts. Such refinementswould be provided in accordance with known and conventional machinedesign practice.

Referring to FIG. 2, the abrasive discs and the spacers may begin assimple circular discs having a center hole which is slightly oversizedso that the discs can be tilted. The discs and spacers are clampedbetween end pieces 3 36 and 38. These end pieces have angularly disposedinner faces 40 and 42, and they establish the desired angle of thediscs. In preferred. form, the shaft 12 has a keyway and key 44 receivedtherein. The discs have appropriate keyways, and so do the end pieces 36and 38, but the latter preferably have two keyways disposed 180 apart,as shown at 46 and 48. In this way the four end pieces may all be alike,but one of the keyways is used for the end piece 36 and the other keywayis used for the end piece 38, thereby reversing the angle, as isdesired.

Referring to FIG. 5, after the discs have been assembled, the edges aredressed as indicated by the broken line 50, so that the edges willconform to the surface of a cylinder.

If desired, the discs and spacers may be preliminarily cemented in faceto face relation to form a single unit. This is illustrated in FIG. 4 inwhich the adjacent faces of the abrasive discs 52 and spacers 54 aremarked to suggest the use of an appropriate cement when assembling thediscs and spacers to form a single unit. The cemented assemblypreferably includes the end pieces 56. Such a unitary assembly may beformed on a mandrel like the keyed shaft, and may be ground or dressedto give it the desired cylindrical surface, and thereafter may behandled as a single unit when mounting the same on a shaft of thesharpening machine. Such cementing is also indicated at 58 in FIG. 5.

The ends 36 and 38 may be die cast. Moreover, under volume manufacturingconditions, the spacers also may be die-cast with their center holes ata slight angle. The abrasive wheels, if molded to final shape, wouldhave their center holes at a slight angle, and would be slightlyelliptical rather than circular, in addition to having an angular edge.This would eliminate or reduce the dressing needed to form the assemblyinto a grinding cylinder.

If desired, the shafts may be relatively adjustable toward or away fromone another, so that a desired overlap of the abrasive disc may bemaintained, even after a reduction in diameter of the disc. Such anarrangement is shown in FIG. 6, in which the abrasive discs 60 and 62are mounted on shafts 64 and 66 driven by gears 68 and 70. The lattermesh with gears 72 and 74 mounted therebeneath. The shaft 66 is carriedat the upper ends of levers, one of which is shown at 76. This lever isoscillatable about the shaft 86 of gear 74, and its position may belocked by means of a locking bolt 78 received in an arcuate slot 80. Bymoving the lower end of levers 76 toward the right, their upper ends aremoved toward the left, thereby overlapping the abrasive discs. It willbe understood that other mountings may be provided to afford suchrelative movement of the shafts 64 and 66.

FIG. 6 also shows that the motor 82 may be operatively connected to gear72 through another gear 84. In this way the motor may be mounted in alowered position as shown, or in an outwardly offset or sidewardposition, not shown.

However, the motor may be connected directly to the shaft 88 of gear 72,as was illustrated in FIG. 3. It is desirable that the motor beassociated with gears that are not adjusted from side to side. In FIG. 6the motor is not affected by the sideward adjustment of the shaft 66.The same would be true if the motor were connected directly to the shaft88.

As so far described the abrasive discs have a single wobble cycle forone full rotation. By the term wobble cycle I mean one reciprocation orone complete back and forth movement. However, the discs may be designedto provide a plurality of wobble cycles for one rotation. In FIGS. 7-11,I show abrasive discs which provide two wobble cycles for one fullrotation.

Referring to FIG. 11 the disc 90, when viewed in section on a diameter9292 is concave-convex, and when viewed in section on another diameter94-94 which is perpendicular to the diameter 9292, is straight, and isperpendicular to the shaft. With such a disc there are two wobble cyclesfor one full rotation. Differently expressed, the entire area of thedisc of FIGS. 2, 4 and 5 slopes in one direction, so that the disc has asingle wobble cycle for one full rotation, whereas in FIG- 11, half thearea of the disc slopes in one direction, and the other half slopes inan opposite direction, so that the disc has two wobble cycles for onerotation. Considered more generally, the disc when viewed in section onone radius is concave-convex; when viewed in section on another radiusis straight; and there are a plurality of such concavo-convex sectionsand a plurality of such straight sections, so that the discs have aplurality of wobble cycles for one rotation. With more than two wobblecycles per rotation the disc might be described as having a sinuous orcorrugated surface.

Referring now to FIG. 9, the knife sharpening machine, as before,comprises two parallel shafts 96 and 98 each carrying a plurality ofabrasive discs 100 and 102 which turn in opposite direction. The discs100 are cemented around hubs 104 which act also as spacers, and thediscs 102 are similarly cemented around hubs 106 which act as spacers.In FIG. 9 the orientation of the discs is such that a diametricalsection is concavo-convex.

FIG. 10 shows the same parts after the shafts 96 and 98 have turned 90.In this orientation a diametrical section is straight and perpendicularto the shaft, as shown. FIGS. 9 and 10 have been drawn with the hubs 104horizontally aligned, and with the hubs 106 horizontally aligned, asbetween the two figures. It will be seen that the overlapped edges ofthe abrasive discs are lower in FIG. 9 than in FIG. 10, showing theaxial movement or wobble of the edges of the discs as the shafts rotate.They wobble up and down in a half revolution, there being two wobblecycles for each full revolution.

On reflection it will be evident that by appropriately shaping the discsthey could provide three or more wobble cycles for each full revolution.

A modified arrangement and orientation of the discs is illustrated inFIGS. 7 and 8. In FIG. 7 the shaft 108 carries discs 110 cemented onspacer hubs 112. These discs are mounted with their concave sidesupward. The shaft 114 has abrasive discs 116 carried by spacer hubs 118.These discs are mounted with their concave faces downward. Moreover, therotative orientation differs from that shown in FIG. 9, in that asection through discs 116 is curved, or differently expressed, the discsare ro ationally displaced by 90 relative to one another. The shaftsrotate in opposite direction as before.

FIG. 8 shows the same parts after rotation through an angle of 90. Adiametrical section through discs 110 is curved, and a diametricalsection through discs 116 is straight.

Here again the hubs 112 have been drawn in horizontal alignment and thehubs 118 have been drawn in horizontal alignment. The overlapped edgesin FIG. 7 are in downward position, and in FIG. 8 are in upwardposition, showing the desired axial reciprocation or wobble movement.The movement is upward in 90 and downward in the next 90, so that thediscs have two wobble cycles for one full rotation.

In FIG. 9 it will be seen that the angle of the sloping area of disc 100is opposite in direction to the angle of a like area of disc 102. InFIG. 7 there is a relative angle because the sloping area of disc 116cooperates with a non-sloping area of disc 110, and vice versa in FIG.8.

It will be understood that shafts 96 and 98 in FIG. 9 may be driven bygearing and a motor as previously described in connection with FIGS. 1through 6, and the same applies to shafts 108 and 114 in FIG. 7. It willalso be understood that spacers may be used between discs in FIGS. 7-10,as shown in FIGS. 16, and that conversely hubs which act also as spacersmay be used inside abrasive discs in FIGS. 16, as shown in FIGS. 710.

It is believed that the construction and method of use of my improvedknife sharpening machine, as well as the advantages thereof, will beapparent from the foregoing detailed description. It also will beapparent that while I have shown and described the invention in severalpre fered forms, changes may be made without departing from the scope ofthe invention, as sought to be defined in the following claims.

I claim:

1. A knife sharpening machine comprising two parallel shafts, meansgearing them for equal rotation in opposite directions, a plurality ofabrasive discs and spacers mounted on each shaft, the abrasive discs onone shaft being slightly overlapped and interleaved with the abrasivediscs of the other shaft, and means securing the coaxial discs on ashaft in parallel relation but with areas thereof at a slight angle tothe perpendicular in order to give the discs a wobble motion as they arerotated by the shaft, the angle of said areas of the discs on one shaftbeing different in direction from the angle of like areas of the discson the other shaft, in which the discs When viewed in section on onediameter are concave-convex, and when viewed in section on anotherdiameter perpendicular to the first diameter, are straight andperpendicular to the shaft, whereby the discs have two wobble cycles forone full rotation.

2. A knife sharpening machine as defined in claim 1, in which atintervals of 90 rotation the straight diametrical sections of the discson one shaft are parallel to the straight diametrical sections of thediscs on the other shaft.

3. A knife sharpening machine as defined in claim 1, in which atintervals of 90 rotation the straight diametrical sections of the discson one shaft are perpendicular to the straight diametrical seections ofthe discs on the other shaft.

4. A knife sharpening machine comprising two parallel shafts, meansgearing them for equal rotation in opposite directions, a plurality ofabrasive discs and spacers mounted on each shaft, the abrasive discs onone shaft being slightly overlapped and interleaved with the abrasivediscs of the other shaft, and means securing the coaxial discs on ashaft in parallel relation but with areas thereof at a slight angle tothe perpendicular in order to give the discs a wobble motion as they arerotated by the shaft, the angle of said areas of the discs on one shaftbeing different in direction from the angle of like areas of the discson the other shaft, in which each of said shafts has a key, and in whichthere are end pieces with angular inner faces between which the discsand spacers are clamped in order to establish the desired angle of thediscs, each of said end pieces have two keyways disposed apart, wherebythe end pieces at one end may be reversed relative to the end pieces atthe other end.

5. A knife sharpening machine comprising two parallel shafts, meansgearing them for equal rotation in opposite directions, a plurality ofabrasive discs and spacers mounted on each shaft, the abrasive discs onone shaft being slightly overlapped and interleaved with the abrasivediscs of the other shaft, and means securing the co axial discs on ashaft in parallel relation but with areas thereof at a slight angle tothe perpendicular in order to give the discs a wobble motion as they arerotated by the shaft, the angle of said areas of the discs on one shaftbeing different in direction from the angle of like areas of the discson the other shaft, in which the discs when viewed in section on oneradius are concavo-convex, and when viewed in section on another radiusare straight and perpendicular to the shaft, there being a plurality ofsaid concaxo-convex sections, and a plurality of said straight sections,whereby the discs have a plurality of wobble cycles for one fullrotation.

References Cited UNITED STATES PATIENTS 1,184,517 5/1916 Burt 51-802,570,690 10/1951 Kilian 51-80 FOREIGN PATENTS 117,696 5/1930 Austria.810,853 8/1951 Germany. 184,796 9/ 1935 Switzerland.

HAROLD D. WHITEHEAD, Primary Examiner US. Cl. X.R.

